(CNN) -- Clashes between tribesmen and government forces near Yemen's Sanaa International Airport on Wednesday led to its closure.
All arriving flights were diverted to Aden, and no flights were taking off from Sanaa, said a Ministry of Transportation official who asked not to be identified because he is not authorized to speak to the news media.
Witnesses said the situation near the airport was chaotic, with explosions, clashes, tribesmen approaching the airport and electricity cut to the surrounding neighborhood.
According to the office of Sheikh Sadeq al-Ahmar, a leader of the main opposition al-Hashid tribe, the government is believed to have cut the electricity.
The flight restrictions were imposed as anti-regime tribesmen battling Yemeni forces occupied the government's news agency compound and the Tourism Ministry in the capital Wednesday, the latest regime entities to be taken over during this week's street battles, witnesses said.
Hundreds of al-Hashid tribal members occupied and surrounded the SABA news agency compound and the tourism building in Sanaa after fighting with government forces in the Hasabah neighborhood.
Other ministry buildings in Hasabah also have been seized. They are the Interior, Trade and Commerce, the Education and the Local Administration headquarters. These and other government buildings in Hasabah were evacuated Tuesday night by the Interior Ministry as fighting raged.
Yemeni state-run television said supporters loyal to the al-Hashid tribe were shelling government facilities.
The fighting broke out after a regionally brokered deal calling for Yemeni President Ali Abdullah Saleh to leave office fell through. Saleh himself is a member of the al-Hashid tribe, a huge and powerful entity with many strands.
After a march Friday, during which dozens of anti-government demonstrators were killed, al-Ahmar embraced the anti-government demonstrators and broke ranks with the president. Since then, more and more tribal members have turned their backs on the president as well.
The violence has attracted international attention.
"We expressed our joint concern on the deteriorating situation on the ground," U.S. President Barack Obama told reporters Wednesday in England with British Prime Minister David Cameron.
The United States is evaluating the security situation in Yemen, but is not moving to evacuate the embassy, State Department spokesman Mark Toner said Tuesday. However, the embassy is permitting employees who want to leave to do so.
U.N. Secretary-General Ban Ki-moon expressed fears that the battles might further destabilize the situation and called for "an immediate end to the fighting" and the continuation of efforts to resolve the country's political crisis.
Saleh's office called media outlets, including Yemen TV, and issued statements from Saleh defending himself.
"I will not be forced by the tribes to enter a civil war," Saleh said. "We will not give in and will fight those who threaten security and stability in the country."
Similar clashes Tuesday killed as many as 41 people -- with both sides claiming casualties. Al-Ahmar said 17 men from the al-Hashid tribe were killed in those clashes. The government said 14 soldiers and 10 civilians were killed.
Yemen, a key U.S. ally in the fight against al Qaeda, has been roiled by protests for most of the year amid anti-government demonstrations that have swept across much of the Arab world. Many of the protesters in Yemen want Saleh to step aside after three decades of rule.
But representatives of the demonstrators who've taken to the streets for months insist their movement is nonviolent and say they will continue a peaceful revolution as the tribesmen and government forces battle.
"The government wants to show the world that our revolution is violent. We tell them no, it is peaceful and will always be peaceful," said Mohammed Saleh Abdullah, a youth revolution leader.
Riyadh Areqi, another youth revolution leader, said protests will continue "under all circumstances until Saleh falls and is held accountable for all his crimes."?
"What is taking place between the al-Ahmar family and government forces does not involve the Yemeni revolution," he said. "Millions are protesting peacefully today around the country while Saleh sheds the blood of the Yemeni people."
Gulf Arab states said Monday that they had suspended efforts to ease the embattled president from office after he once again balked at signing a deal with opposition leaders.
In a statement carried by the Saudi Press Agency, foreign ministers with the Gulf Cooperation Council said they were dropping the deal "for lack of appropriate circumstances for agreement."
The council is made up of representatives from the United Arab Emirates, Bahrain, Saudi Arabia, Oman, Qatar and Kuwait.
Under its plan, Saleh would have ceded power to a transitional government after 30 days.
At his meeting Wednesday with Cameron, Obama noted that Yemenis want a "more unified and more secure" nation and "greater opportunity and prosperity."
"We are proud of the leadership of the Gulf Cooperation Council in seeking an orderly and peaceful resolution to the crisis, and we call on President Saleh to move immediately on his commitment to transfer power."
Opposition leaders signed the pact Saturday, but Saleh said he would not go along unless the opposition re-signed the agreement at a public ceremony at his presidential palace, which was surrounded by armed pro-government protesters.
Opposition members have long contended that Saleh had no intention of signing the agreement.
Saleh said Wednesday that he's "willing to sign the proposal, but on the basis of dialogue."
"I will not give any more concessions in order to step down," he said.
Journalist Jeb Boone contributed to this report.